The present invention relates to a latch. More particularly this invention concerns a latch used in a motor vehicle.
A standard motor-vehicle door latch has a housing attached to a door edge and holding a pivotal fork that can move between a latched position engaged around a bolt extending from a doorpost and a released or unlatched position allowing the latch to move relative to the bolt. When latched, the door is held closed, when unlatched or released it can be opened. As a rule the fork is retained in the latched position by a pawl which is pivotal to release the fork.
In turn this pawl is typically displaced by a release lever. An actuating lever typically moved by an inside and/or outside door handle is coupled through a mechanism with the release lever to operate same and unlatch the door. Another locking lever is connected to the mechanism and can, in a locked position, set the mechanism so no movement is transmitted from the actuating lever to the release lever and, in an unlocked position, set the mechanism so the actuating lever operates the release lever. This is described in detail in German utility model 299 13 464 published Jan. 20, 2000 and in European patent 0,475,037 published Oct. 6, 1993.
In a central-locking system such as described in German patent 196 32 781 the locking lever can be moved between its locked and unlocked positions by a servomotor that is controlled centrally. Thus all the vehicle""s doors can be locked and unlocked simultaneously. In addition an antitheft function is added which in an antitheft-on mode prevents manual actuation of the door latches at least from inside the vehicle. Although normally even a locked door can be open from inside, in the antitheft-on mode this is impossible. Thus, for instance, a thief who breaks a vehicle window and reaches inside cannot open the vehicle door.
In order to make such a latch resistant to forced entry, it is necessary to provide a complex linkage between the part inside the door that is capable of unlocking the door and the appropriate mechanism. This linkage and the part operating it can be somewhat complex, thereby adding considerably to the cost of the latch. What is more the standard lock button or lever is susceptible to manipulation from outside, for instance by a wire inserted past the door seal, so such systems offer inadequate security.
Accordingly it is known from German utility model 296 08 002 published Aug. 22, 1996 to use the inside door handle to operate the locking mechanism. Thus when the door is locked a first actuation moves the locking lever into the unlocked position and a subsequent actuation opens the door. Such systems have the advantage of apparent simplicity, but are invariably reliant on complex linkages comprising quite a few moving parts.
It is therefore an object of the present invention to provide an improved motor-vehicle door latch.
Another object is the provision of such an improved motor-vehicle door latch which overcomes the above-given disadvantages, that is which accommodates, if necessary, an antitheft function and that is nonetheless of simple and inexpensive construction.
A motor-vehicle door latch has according to the invention a housing, a part displaceable relative to the housing to release the latch, and mechanism on the housing operable to displace the part and release the latch. An actuating lever is pivotal on the housing between an unactuated position and an actuated position and a locking lever is also pivotal on the housing between a locked position coupling the actuating lever with the mechanism to displace same and an unlocked position uncoupling the actuating lever from the mechanism. In accordance with the invention respective formations directly formed on the actuating lever and on the locking lever are directly engageable with each other for displacing the locking lever into the un-locked position on displacement of the actuating lever into the actuated position.
Thus with this system the locking lever and actuating lever are constructed that, when the locking lever is in the locked position, operation of the actuating lever will directly move the locking lever into the unlocked position. Otherwise such operation of the actuating lever in the unlocked position of the locking lever will have no effect at all. Once the actuating lever has been moved to unlock the latch, a subsequent actuation of the actuating lever will serve to actually release the latch and open the door. No complex linkages are needed, merely two formations on the actuating and locking levers that are position such that they are engageable with each other only when the locking lever is in the locked position. The actuating lever can be unitary with or linked to an inside door handle.
According to the invention the formations include a tongue formed directly on one of the levers and an abutment formed on the other of the levers. The levers are pivotal about respective axes and the tongue extends radially of the axis of the respective lever. Furthermore the abutment has a rounded edge directly engageable with the tongue. Thus the two parts slide silently and smoothly on each other.
According to the invention an antitheft system is connected with the mechanism to prevent coupling of the release lever with the part. Thus when the antitheft system is in the on condition, no matter how many times the actuating lever is operated the latch will not be released.
The mechanism according to the invention includes a coupling link carried on the locking lever. The antitheft system holds this coupling open.
The mechanism according to the invention includes a release lever formed with an L-shaped slot having one leg extending angularly of a pivot axis of the locking lever and another leg extending radially of the pivot axis and directly engageable with the part and a coupling lever slidable on the locking lever and having a pin engaged in the slot for, when engaged n the one leg, connecting the locking lever to the release lever and, when engaged in the other leg, for allowing the locking lever to pivot relative to the release lever.